Laboratory Study on the Use of Produced Water in Crosslinked-Gel-Based Hydraulic Fracturing

Fracturing fluids are commonly formulated with fresh water to ensure reliable fluid rheology. However, fresh water is becoming more costly, and in some areas, it is difficult to obtain. Therefore, the use of produced water in hydraulic fracturing has received increased attention in the last few years. This study investigates the feasibility of using field-produced water to formulate crosslinked-gel-based fracturing fluid through a series of laboratory experiments. Research applied three different approaches to qualify the produced water for the formulation of the fracturing fluid: 1) dilution of the produced water with fresh water, 2) reduction of water cations’ concentrations, and 3) use of different chelating agents. The fracturing fluid was prepared with the typical fluid additives used in the field. Compatibility tests were done to examine the compatibility of the water with the fracturing fluid system, and the fracturing fluid viscosity was evaluated through high-pressure high-temperature (HP/HT) viscosity measurements. Results show that produced water could cause formation damage if used directly to formulate the hydraulic fracturing fluid. Precipitations could be prevented if the produced water is diluted with fresh water, or treated to reduce the concentration of scale-forming ions. Produced water could be used to formulate the fracturing fluid if diluted with fresh water 25 times; and the concentrations of Ca and Mg ions that the system can tolerate were found to be 400 and 25 ppm, respectively. Further reduction of divalent cations indicated the enhancement of the fracturing fluid viscosity. The use of HEDTA and GLDA was found to increase the system tolerance to Ca and Mg ions, and to maintain adequate fracturing fluid viscosity. However, sodium gluconate, di-sodium EDTA, and di-ammonium EDTA showed a breaking effect on the viscosity of the fracturing fluid. This work contributes to the understanding of the main factors that enable the use of produced water for hydraulic fracturing operations. Maximizing the use of produced water could reduce its disposal costs, mitigate environmental impacts, and solve fresh water acquisition challenges